Nanofiltration Membranes for High‐Selectivity Separation of Li ⁺ and Mg ²⁺ From Salt Lake Brines: Strategies, Challenges, and Perspectives

ABSTRACT Against the backdrop of global clean energy transition and surging demand for lithium resources, lithium extraction from salt lakes presents unprecedented development opportunities. Nanofiltration (NF) membrane technology, recognized for its efficiency, energy savings, and environmental benefits, demonstrates significant application potential in lithium extraction from salt lake brines, particularly for the critical Mg 2+ /Li + separation step in high Mg 2+ /Li + ratio brines—a key resource. However, substantial challenges remain. This review systematically summarizes recent research advances in the core separation mechanisms of NF membranes for Mg 2+ /Li + separation and strategies for membrane structural design optimization. It prospectively analyzes key bottleneck issues, including membrane fouling, long‐term operational stability under extreme brine environments, and the economic viability of large‐scale applications. Furthermore, future research directions are highlighted, emphasizing the need to focus on machine learning‐assisted membrane design, the development of advanced anti‐fouling coatings, and integrated technologies coupling NF with processes such as electrodialysis or adsorption. This review aims to provide technical references for the efficient exploitation of salt lake lithium resources and offer scientific guidance for the development of next‐generation high‐performance NF membranes.